1. Field
Provided are a modified microorganism for high efficient production of lactic acid, an expression vector for constructing the modified microorganism, and a method of producing a lactic acid using the same.
2. Description of the Related Art
Lactic acid is an organic acid that plays a role in various industry such as cosmetics, chemical, metal, electronic, textile, dyeing and pharmaceutical industry as well as in various food additives such as preservatives, flavoring agents and acidulents. Further, lactic acid is used also as a monomer for producing polylactic acid (“PLA”), which is a biodegradable plastic. Recently, this kind of plastic is a good option for substituting conventional plastic produced from petroleum oil because of low emission of carbon dioxide.
Specifically, lactic acid has a hydroxyl group and a carboxyl group, making it greatly reactive such that it plays a important role as a source material on producing chemical including acetaldehyde, polypropylene glycol, acrylic acid, 2,3-pentathione as well as polylactic acid. Lactic acid is also used for producing ethyl lactate, which is a biodegradable and non-toxic solvent and used in electronic manufactures, paint or textile industry, detergents or printing industry.
Recently, strains of Kluyveromyces are being considered as viable alternatives to Saccharomyces cerevisiae. Kluyveromyces marxianus and Kluyveromyces lactis are classified as GRAS (“Generally Recognized As Safe”) microorganisms, and may therefore be used with the same security as Saccharomyces cerevisiae. 
K. marxianus is reported to grow at a temperature of 47° C., 49° C., and even 52° C., and shows superior acid resistance. Therefore, attention has been paid to K. marxianus as an organic acid- and platform compound-producing strain.